Conventionally, technology for improving the braking performance on snow and the braking performance on ice by providing a plurality of blocks 120 on a tread surface 110 of a pneumatic tire 100, and forming a plurality of sipes 130 in each block is known, as illustrated in FIG. 7. However, in the pneumatic tire 100, the groove area is large, so the tire ground contact area is reduced. As a result, the braking performance on ice was not sufficient.
Therefore, in the pneumatic tires disclosed in Japanese Unexamined Patent Application Publication No. H11-342706 and Japanese Unexamined Patent Application Publication No. 2009-241626, a tread pattern that combines blocks and ribs is adopted in order to improve the braking performance on snow and the braking performance on ice in a balanced manner.
However, in the pneumatic tire disclosed in Japanese Unexamined Patent Application Publication No. H11-342706, the ribs are provided on only one side in the tire width direction (vehicle mounting outer side), so there is a possibility that the braking performance on ice cannot be improved sufficiently. Also, in the pneumatic tire disclosed in Japanese Unexamined Patent Application Publication No. 2009-241626, the blocks are provided only on both outer sides in the tire width direction (shoulder regions), so there is a possibility that the braking performance on snow will be greatly reduced.